1. Field of the Invention
This invention relates to a semiconductor memory device wherein memory cells used for a readable/writable volatile memory such as a Dynamic Random Access Memory (hereinafter called a "DRAM") and memory cells used for a read-only non-volatile memory like a ROM (Read Only Memory) such as an Electrically Programmable Read Only Memory (hereinafter called an "EPROM"), an Electrically Erasable Programmable Read Only Memory (hereinafter called an "EEPROM"), a mask read only memory or the like, are formed within a single memory cell array.
2. Description of the Related Art
A semiconductor integrated circuit having a ROM and a RAM (Random Access Memory) provided within a single chip has recently been manufactured in products with the advance of its high integration.
This type of semiconductor integrated circuit has been disclosed in Japanese Patent Application Laid-Open Publication Nos. 60-47294 published on Mar. 14, 1985, 64-8591 published on Jan. 12, 1989 and 3-269894 published on Dec. 2, 1991.